On its own, killing @ is a small move. Few other social media networks use @ as a way of indicating who you're talking to.

But at Twitter, @ is at the core of a crucial debate within the company about how to get Twitter's user-base growing again. Some people — including CEO Dick Costolo — think the shorthand codes used on Twitter may be deterring new users from joining the site. Unless you already know what they mean, terms like @, #, RT, MT and #FF are meaningless.

They look like computer code, and if there's one thing that ordinary users hate, it's code. Ordinary users are Twitter's future: the millions of people Twitter needs to join and stick with the company in order to get meaningful growth in the years to come.

But in terms of attracting those ordinary people, Twitter is currently dead in the water: The service added only 1 million users in the U.S. last quarter, bringing its American audience to 54 million. Twitter had 241 million users worldwide in Q4 2013, adding only 9 million in total from the prior period.

On Twitter's last earnings call, the company's stock tanked despite good financial results when it became clear that "timeline views" — a key measure of user engagement — had actually declined.

Costolo was hammered by analysts on that call wanting to know whether the company had a grip on its flagging user stats. Costolo told them he was running several experiments on Twitter to make the service simpler and easier for new users to get on board.

He explained that Twitter was aware that new users had difficulty figuring out the best ways to use Twitter, and the company was working on making it easier so that they "get it" instantly: "It's not just 'get it' in the first weeks or months on Twitter, it's 'get it' on the first day on Twitter ... so that's a focus."

Unlike Facebook, which asks for obvious information and then uses it to make obvious connections, Twitter demands significant time and energy from the user up front. It doesn’t fully succeed in telling you how to use the service; it fails, utterly, to tell why you should. Those willing to stick around long enough are rewarded with a peculiar sense of something that could best be described as belonging.

“That language and scaffolding can be confusing and opaque,” Costolo said. To solve the problem of so-called Twitter quitters who log in once and never come back, he said, it needs to be “clear and simple.”

Whether @ lives or dies may seem trivial. But @ may in fact turn out to be key to saving Twitter. If 1 billion try and then abandon Twitter because they can't be bothered learning the difference between "@" and ".@" — note the period! — then Costolo would have to admit that Twitter is broken as long as it remains dependent on code symbols.

Correction: This story originally said that 1 billion people had tried Twitter and stopped using it. That was incorrect. About 1 billion people have tried Twitter and of that number around 700 million stopped using it. Our fault! Sorry.